China's national observatory on Saturday morning renewed its yellow alert, the third-highest level of warning, for smog here.

Moderate smog will fall over Beijing and northeast Hebei province from Saturday morning to Sunday morning, with some areas to see heavy smog, Xinhua news agency cited the National Meteorological Centre (NMC) as saying.

Residents are advised to take protective measures and those with respiratory diseases should reduce outdoor activities, NMC said.